cant sort out the problem(dhadley pls reply

[nitro9]

1975 70 hp johnson, runs ok at 1/3 throttle after that bogs out, cleaned and rebuilt carbs ( carb cleaner and compressed air) no change!played with throttle and choke while running and found happy running sequence, checked all fuel lines checked diaphram in pump, all is good,boat shop says johnson carbs can become porous?what do u think<br /><br />please whats your opinion<br />and possible soulution.

 

[fireman57]

Re: cant sort out the problem(dhadley pls reply

If you found a happy running sequence with the choke then it has to be fuel. Are you sure that you got the high speed jets absolutely clear? You may have also brought more junk from your tank to your carbs. You may look for Joe Reeves thread on setting these carbs. Could just have one misadjusted. Could still have an air leak. One of the pros here (sorry, can't remember who) puts grease on one connection at a time starting at the tank and if the problem clears up then he knows where the leak is and replaces either the line or the clamp there. You may try borrowing a known good fuel line and primer bulb and run it to see if that solves it.

 

[Dhadley]

Re: cant sort out the problem(dhadley pls reply

I dont think its so much that they become porous as the throttle shaft wears the carb body and they can pull air there. There were a lot of bulletins out about that time about jetting. They were just getting into the EPA stuff and were tryibng to pull fuel out to gain EPA credits. Since the 3 cylinder was one of, if not the best selling motor that was the quickest way to earn credits.<br /><br />Go over your sync-n-link to make sure its right. Make sure you have fresh fuel and Champion plugs. If all that is OK then you may have to rejet. No big deal if you have a selection of jets.

 

[nitro9]

Re: cant sort out the problem(dhadley pls reply

took the boat to the shop and had a dyno done and ran good for them in the dunk tank, talking about rejetting. please more info

 

[nitro9]

Re: cant sort out the problem(dhadley pls reply

could the water pump have any effect on this problem?